Breath of Clarity

Ecology Discussion #3: A

The role of biogeochemical cycles can be summarized by the input and output of essential elements for living organisms. The biogeochemical cycle provides a pathway for movement of the essential elements. The role of biogeochemical cycles is to balance the levels of essential elements in a life-sustaining way, all while recycling and conserving the matter. Crucially, biogeochemical cycles regulate the essential elements by restoring a given ecosystem to function at its proper state, equilibrium. Therefore, a role of biogeochemical cycles is to manage waste so it is reused again. For example, when a living organism dies and decays, it disintegrates, and its components are repurposed. Further, biogeochemical cycles enable the transfer of matter from one form to another, such as the hydrological cycle transfer of ice into water. The biogeochemical cycles also transfer matter from one locality to another such as nitrogen in the atmosphere versus nitrogen in the soil. Biogeochemical cycles also facilitate the storage of elements. For example, through the nitrogen cycle and with the help of the nitrogen fixing bacteria, green plants are able to utilize nitrogen in bits though it is abundant in the atmosphere. Essentially, the biogeochemical cycles direct the flow of life-giving nutrients.

I would explain phosphorous (P) and nitrogen (N) effecting water quality downstream from a city in terms of biogeochemical cycles. As the textbook illustrates, rivers are sensitive to changes in P and N inputs. While nitrogen uptake provides nutrients supporting growth of vegetation and animal populations, too much nitrogen is harmful to the ecosystem. Excessive nitrogen results in overload of algae which then decreases water quality. Aquatic populations cannot survive because there is not enough oxygen. Therefore, the wastewater engineer shares the balancing role biogeochemical cycles have. However, I would not recommend Leopold’s Odyssey as a way to sway the engineer’s thinking. While Leopold showed biogeochemical cycles function to balance the ecosystem, Leopold’s Odyssey was communicating the resiliency of biogeochemical cycles regardless of environmental stewardship (Leopold 2013). I would instead use Leopold’s Odyssey to show people global climate change would kill off the human race, seeing the species as having a temporary existence in the grand scheme of all life types, rather than killing the planet (Leopold 2013). There are other Leopold essays emphasizing humans being a part of nature and having a role in regulating conditions that would be more appropriate to recommend. Also, I would recommend a study from the Journal of Global Biogeochemical Processes highlighting the role of biogeochemical modeling in quantification of sediment-water interactions in a polluted river. The river discussed in the study is subject to high levels of domestic wastewater inputs from a metropolitan area (Trinh et al. 2012). The study shows the beneficial impact of improved wastewater treatment. The study’s results uniquely emphasize the importance of sediments as a potential removal mechanism of organic matter and nutrients from the water column in this type of highly impacted urban river, further demonstrating that rivers need to be considered as reaction sites and not just as inert conduits (Trinh et al. 2012). It details how to do the chemical analysis and reactive transport modeling which is particularly relevant and applicable to the engineer’s project.


Leopold, Aldo. 2013. “A Sand County Almanac & Other Writings on Ecology and Conservation.” New York: The Library of America.

Trinh, Anh Duc, Filip Meysman, Emma Rochelle-Newall, Marie Paule Bonnet. 2012. “Quantification of sediment-water interactions in a polluted tropical river through biogeochemical modeling”. Global Biogeochemical Cycles. 26 (3).

Response by Josh Mabis:

Hi Mary,

Great job on your post. I think one of the things I would try to explain to the wastewater engineer is that agriculture isn’t the only thing to be wary of when thinking about N and P, even though that’s the first thing I think of. Human waste is also a big issue when it comes to decreases in water quality. As more and more people have been living in cities the growth in wastewater has had a very negative impact on water quality. That is one of the things that NOAA has been researching when it comes to water quality: “Because there are increasingly more people living in coastal areas, there are more nutrients entering our coastal waters from wastewater treatment facilities, runoff from land in urban areas during rains, and from farming” (NOAA 2019).


NOAA. 2019. “What is nutrient pollution?” Last modified October 22, 2019. to an external site.

My Comment:

Hi Josh,

Great job in explicitly identifying multiple sources of the issue in water quality. With the research from NOAA in hand, what approaches may be useful for the wastewater engineer to take particularly considering the scientist cannot control the trend of an expanding human population?

Response by Professor Fenton Kay:

Great response, Mary. Also a nice catch on the article. I’m inclined to agree with you regarding how to convince a wastewater engineer. A well-presented article with modeling and bunches of math seems like the thing that might well catch the engineer’s attention.

You mention that there are other readings among Leopold’s essays that might be better than Odyssey. Can you specify one of those that you are especially fond of?



My Comment:

Hi Fenton,

Definitely, engineers have that analytical personality type. All the math involved in the article would resonate well with them.

After your question, I looked over the table of contents to see whether any were particularly pertinent to water quality and the work of wastewater engineers. The chapter “The Round River: A Parable of Conservation” stuck out to me. I flipped to the first page and read the fourth paragraph about seeing a river from a framework of specialization versus as its entire stream. Due to the nature of most engineer minds, reading this chapter may sway the engineer’s thinking in terms of having him examine the collective behavior of biotic materials. It is similar to the way our class is perceiving the job in terms of biogeochemical cycles. The text stresses the specialized framework equips the engineer with facts about the soils, floras, and fauna separately but do not necessarily deeply inform the engineer about how to interpret the current. For example, the biotic stream is capable of flowing in long or short circuits, rapidly or slowly, uniformly or in spurts, in declining or ascending volume. Further, in the eighth paragraph, Leopold explains the transmission of energy usually perceived as a food chain is more accurate to be viewed as a pipeline because there are leaks at every joint. Due to the spillage in route, only part of the energy in any stage reaches its maximum capacity. That said, the essay is useful in terms of addressing nuances any engineer may not have previously approached the project with.


Leopold, Aldo. 2013. “A Sand County Almanac & Other Writings on Ecology and Conservation.” New York: The Library of America.

Response by Amy Zobler:


Your description of biogeochemical cycles was very descriptive. Relating it to an equilibrium and stressing how all wastes produced need to be able to be recycled in the ecosystem is a great way to convince others of the importance of proper wastewater management. The case study and specific examples you mentioned are also great ways to illustrate this point. Do you think Trinh’s study prioritizes mitigation efforts to control large influxes of nutrients over prevention efforts to decrease these high levels of problematic nutrients in the first place? Would the mitigation efforts be enough to control the problem?

Trinh, Anh Duc, Filip Meysman, Emma Rochelle-Newall, Marie Paule Bonnet. 2012. “Quantification of sediment-water interactions in a polluted tropical river through biogeochemical modeling”. Global Biogeochemical Cycles. 26 (3).

Comment #1:

Orignal Post by Sofia Maldonado:

Biogeochemical cycles are how nutrients are moved through ecosystems. Energy from the nutrients move through levels in the food chain giving biota what they need to function (Chapin III et al. 2011).

If I were an environmental professional, I would first explain that phosphorus and nitrogen are important nutrients in any water cycle. However, too much of these in a water system can cause negative affects. As these elements flow downstream, they, specially nitrogen, can become more concentrated, especially when passing near a city where net anthropogenic nitrogen inputs increase due to an increase in human population (Howarth et al. 2012).

It would be best to have routine water checks to make sure there hasn’t been a rise in any one element.

I may recommend Leopold’s “Odyssey” to the engineers but would explain to them it is a metaphor for how phosphorus and nitrogen may travel though the watershed. I would only offer it to them as a supplement to hard facts.


Chapin III, F. Stuart, Pamela A. Matson, and Pater M. Vitousek. 2011. Principles of Terrestrial Ecosystem Ecology. 2nd Ed. New York: Springer. E-Book.

Howarth, Robert, Dennis Swaney, Gilles Billen, Josette Garnier, Bongghi Hong, Christopher Humborg, Penney Johnes, Carl-Magnus Mörth, and Roxanne Marino. 2012. “Nitrogen fluxes from the landscape are controlled by net anthropogenic nitrogen inputs and by climate.” Frontier in Ecology and Environment 10:36-43, doi: 10.1890/100178.

Leopold, Aldo. 2013. Sand County Almanac & Other Writings on Conservation and Ecology. New York: The Library of America.

My Comment:

Hi Sofia,

A particular strength of your post is the mention of how a downstream flow direction plays a critical role in the engineer’s project. For a project in another class, I looked at how the Klamath river’s health impacted its salmon population. Research identified a strong negative relationship between dissolved organic matter (DOM) and ecosystem function by using strategy such as photo-degradation, complexation, sorption, microbial processing, and mineralization (Oliver et al 2016). Human impoundments influence the spatial dynamics of the river’s DOM which significantly alters its flow (Oliver et al 2016). The salmon suffer consequence due to inconsistency in regards to nutrient cultivation and transport (Oliver et al 2016). I imagine routine water checks coupled with policy change could have prevented the Klamath river being declared a coho salmon critical habitat.

In the case water checks are implemented and the action detects imbalance in P or N, how can it be efficiently rebalanced on demand?


Oliver, Alison, Robert G. M. Spencer, Michael L. Deas, Randy A. Dahlgren. 2016. “Impact of Seasonality and Anthropogenic Impoundments on Dissolved Organic Matter Dynamics in the Klamath River (Oregon/California USA)”. Geophysical Research: Biosciences.

121 (7). pp: 1946-1958.

Response by Sofia Maldonado:

Hi Mary,

Thank you and that is an amazing example of the importance of knowing about your water system. And great question! First it would be beneficial to determine specifics of the imbalance (i.e. excess amounts or depleted amounts). This could be done by taking water samples all the way up the water shed until the location where the change happens is found. Once the source has been identified, actions can then be taken to find a way to meditate the imbalance. For example, a team from USGS published a paper recently regarding excess amounts of phosphorus being related to agricultural runoff. The excess came from fertilizer and manure applications, which are important in growing crops efficiently (U.S. Geological Survey, 2019). Knowing the amount of phosphorus that would keep the water system working properly and knowing the amount of excess phosphorus being released by farming will both be helpful in mitigation plans that can balance the inputs and outputs of phosphorus in the water system (U.S. Geological Survey, 2019). This might include changing to less synthetic fertilizers and manure.


U.S. Geological Survey. “Investigating the Effects of Historical Phosphorus on Current River Quality.” December 16, 2019. Accessed October 2, 2020.

My Reply:

Hi Sofia,

I agree it is important to specify the imbalance to inform action steps. Your explanation of taking water samples reminds me of grid sampling. Finding the source is a stellar strategy. Awesome article- it is so applicable to the topic being discussed. It is interesting to see the agricultural runoff explicitly conveyed as from fertilizer and manure applications.